Institute for Complex Engineered Systems Embedded and Reliable Information Systems Laboratory Sensors and Sensor Networks Mike Bigrigg March 16/18, 2004

Institute for Complex Engineered Systems Embedded and Reliable Information Systems Laboratory Sensors/S’nets Intro  Cannot just measure anything  Analog is dirty; Digital is clean and pretty  Secondary data is important in order to answer the “why” questions  Sensor network management systems have costs too! Sometimes lots!

Institute for Complex Engineered Systems Embedded and Reliable Information Systems Laboratory Motion Detectors Motion detectors do not detect motion

Institute for Complex Engineered Systems Embedded and Reliable Information Systems Laboratory Sensor Components  Detector  Has a material change based on physical phenomena  Analog-to-Digital Conversion  Electronics can measure resistance and frequency  Processing  Analog isn’t pretty

Institute for Complex Engineered Systems Embedded and Reliable Information Systems Laboratory Simple Temperature Sensor 20KΏ Resistance of the material changes based on temperature

Institute for Complex Engineered Systems Embedded and Reliable Information Systems Laboratory Simple Temperature Sensor 30KΏ

Institute for Complex Engineered Systems Embedded and Reliable Information Systems Laboratory Simple Temperature Sensor 10KΏ

Institute for Complex Engineered Systems Embedded and Reliable Information Systems Laboratory Thermostat (Mechanical Sensor)  Bimetal plate in a spiral. Grows as the temperature expands one side faster than the other side. on off

Institute for Complex Engineered Systems Embedded and Reliable Information Systems Laboratory Computer Data Acquisition Sensor Devices  Analog  Microphone  Gameport  Digital  Serial/USB  Parallel  Other  Special PCI card Otherwise most sensors tied directly to actuator (e.g. home thermostat)

Institute for Complex Engineered Systems Embedded and Reliable Information Systems Laboratory Commercial Sensors  $150-$15000 Logger Interface to Computer Wireless MOTES

Institute for Complex Engineered Systems Embedded and Reliable Information Systems Laboratory CMU Critter Sensor

Institute for Complex Engineered Systems Embedded and Reliable Information Systems Laboratory Analog Data Data not very smooth Commercial sensors not like this

Institute for Complex Engineered Systems Embedded and Reliable Information Systems Laboratory Degree Changes Between Readings  9 Degrees  2  4 Degrees  262  3 Degrees  622 Good? Bad? Data Set A 10x / minute 1 week; June 2003

Institute for Complex Engineered Systems Embedded and Reliable Information Systems Laboratory Why not more identical? Why such a big range? Two Sensors; Same Room

Institute for Complex Engineered Systems Embedded and Reliable Information Systems Laboratory Pattern? 10x / minute ; 1 week

Institute for Complex Engineered Systems Embedded and Reliable Information Systems Laboratory Correlated Pattern? Why?

Institute for Complex Engineered Systems Embedded and Reliable Information Systems Laboratory Support Administration  ECE Facilities Group  Supports 2,000 machines  Staff of 10 full time sysadmins  (Plus CMU Network support)  Sensor Installation  Sensor Maintenance/Replacement

Institute for Complex Engineered Systems Embedded and Reliable Information Systems Laboratory Storage Costs  10 x / minute (10 bytes per reading)  500MB a year  2,000 sensors = 1TB a year (1,000GB)  (Times number of sensor types)  (Times lifetime – historical trends)  (Times backup! Offsite storage?)  Plus server plus network plus … ~$1/GB

Institute for Complex Engineered Systems Embedded and Reliable Information Systems Laboratory CMU Critter Sensor PRICESLESS! Everyone else paying for the support PRICESLESS! Thermistor $0.70 Wire $0.02 Connector $0.30

Institute for Complex Engineered Systems Embedded and Reliable Information Systems Laboratory Lifetime Costs  Hoover Dam  What sensors?  Costs?  Lifetime?

Institute for Complex Engineered Systems Embedded and Reliable Information Systems Laboratory Lifetime Costs II  Highway system  What sensors?  What costs?  Inertia of system  Upgrades  Replacement  Degradation